Electrical switch unit with thin strip mount and sequentially operated snap switches



Dec. 13, 1966 A. T. c. BURROWS 3,291,933 ELECTRICAL SWITCH UNIT WITHTHIN STRIP MOUNT AND SEQUENTIALLY OPERATED SNAP SWITCHES 4 Sheets-Sheet1 Filed Oct. 15. 1965 FIG! U 2666 o o 5 2'7 27 26b 26b 34d Z0 Z0flvf/wve flew/m? 77/0/1445 4492155 31/220015 Dec. 13, 1966 T c. BURROWS3,291,933

A. ELECTRICAL SWITCH UNIT WITH THIN STRIP MOUNT AND SEQUENTIALLYOPERATED SNAP SWITCHES Filed 0C(.. 15, 1965 4 Sheets-Sheet 2 MM flag14AM Dec. 13, 1966 A. T. c. BURROWS 3,291,933

ELECTRICAL SWITCH UNIT WITH THIN STRIP MOUNT AND SEQUENTIALLY OPERATEDSNAP SWITCHES 4 Sheets-Sheet 5 Filed Oct. 15. 1965 14 7p A/E Y5 Dec. 13,1966 A. T. c. BURROWS 3,291,933

ELECTRICAL SWITCH UNIT WITH THIN STRIP MOUNT AND SEQUENTIAL-LY OPERATEDSNAP SWITCHES Filed Oct. 15. 1966 4 Sheets-Sheet 4 i/z f/wv/e' Jg THZIE$701 096 flwezas @EFM/ 977- z vfs s United States Patent ()flice3,291,933 Patented Dec. 13, 1966 ELECTRICAL SWITCH UNIT WITH THIN STRIPMOUNT AND SEQUENTIALLY OPERATED SNAP SWITCHES Arthur Thomas CharlesBurrows, Stevenage, England, assignor to Geo. W. King Limited,Stevenage, Hertfordshire, England, a British company Filed Oct. 15,1965, Ser. No. 496,581 Claims priority, application Great Britain, Nov.13, 1964, 46,423/ 64 14 Claims. (Cl. 200-76) This invention relates toelectrical switch units.

In the case of an electrically operated hoist the electric motor fordriving the winding drum will, when the hoist is in its operativeposition, normally be located at an elevated position out of easy reachof an operator at floor or ground level and it is convenient thereforeto provide a so-called pendant switch unit which will hang down from thehoist and will be located at such a level that an operator standing onthe floor or ground may readily control the operation of the hoistmotor. Since such a switch unit is suspended its weight and facility ofoperation are features of considerable importance.

It is the primary object of the present invention to provide an improvedpendant switch unit which is relatively light in weight and of compactconstruction such that it will be capable of being readily held in andmanipulated by one hand thus leaving the other hand of the operator freefor load control or other purposes. It is a further object to provide aswitch unit so designed that the risk of wrong actuation by an operatorwill be reduced to a minimum.

According to the present invention there is provided a switch unitcomprising two strip like elements so formed and relatively so arrangedas to provide spaced parallel supporting means at least one of which isadapted to support two or more pairs of fixed electrical contacts atspaced locations therealong, two or more plunger members supported inspaced relation by said pressings for sliding movement transversely withrespect thereto and a pair of contact carriers pivotally mounted on eachplunger member in such a manner as to be disposed in the space betweenthe aforesaid strip like elements, such contact carriers being springloaded and so arranged on their respective plunger members that upondepression of either plunger member the contact carriers associatedtherewith will be moved angularly past a dead centre position whereafterthe spring will be effective to cause them to snap into a positionwherein the contacts carried thereby will bridge the appropriate pair offixed contacts carried by the aforesaid supporting means. Preferably theplunger members will be actuated through the medium of depressible pushbutton elements appropriately disposed in an outer casing housing theswitch mechanism and springs or the like will be associated with saidplunger members, which springs will be effective to restore the plungermembers, and their associated contact carriers to their initialpositions upon release of pressure on said push button elements.Preferably also interlocking means will be incorporated to preventsimultaneous actuation of the plunger members, i.e., when one pushbutton element is depressed the plunger member with which the other pushbutton element is associated will be positively prevented from operativemovement.

In order that the nature of the invention may be more readily understoodreference will now be made to the accompanying drawings which show oneembodiment by way of example and in which:

FIGURE 1 is a front elevational View of a switch assembly partiallybroken away to permit of illustration of various constructionalfeatures,

FIGURE 2 is a sectional view on a horizontal plane,

FIGURE 3 is a longitudinal sectional view, the plane of the sectionbeing varied, the better to illustrate constructional details,

FIGURE 4 is a schematic diagram illustrating a switch assembly such asis illustrated in FIGURES 13 connected in the control circuit of areversible electric motor,

FIGURES 5 and 6 are respectively a side elevational and plan view of apressing from which switch body components may be produced.

Referring now to the drawings 10, 11 and 12 denote three parts of anouter casing adapted to house the switch mechanism, such partscomprising metal pressings which are provided with a coating of plasticor other dielectric material of the order of .020" thick. Interposedbetween the aforesaid parts on assembly thereof are annular sealingrings 13 formed of rubber or other appropriate mate-rial. It will benoted that the upper end casing part 10 is formed with an enlarged holeadapted to accommodate a cable sleeve 14 while the central or main part11 is provided with two depressible switch operating elements 15 eachformed of rubber or other appropriate material. Each of the elements 15.conveniently carries a plate 16 marked, as will be clearly seen fromFIGURE 1, to indicate the function of the switch, such plate being inturn covered by a transparent disc or the like 17 adapted to constitutea window.

Located within the aforesaid outer casing is the actual switch unitwhich comprises two steel pressings 18, 19 adapted to support aplurality of contacts 20 which are appropriately disposed in pairs.Supported in the pressings 18, 19 for limited sliding movementtransversely with respect thereto are three plunger members 21, 22 and23 each of which is urged by a separate spring 24 into its normal or atrest position, i.e., is urged to the right as shown in FIGURE 3. Theupper and lower members 21, 23 are identical and each is so arrangedthat one of the depressible operating elements 15 will register andcooperate therewith. Moreover each of the members 21 and 23 is providedwith a cantilever projection one of which is indicated at 25 (FIGURE 3)adapted to cooperate with the central plunger member 22 as will behereinafter more fully described. As shown the member 23 is providedwith an upwardly directed projection 25 but it will be appreciated thatin the case of the member 21 such projection will be directed downwardlyas indicated in FIGURE 1. The centre plunger member 22 while beingsimilar to the members 21 and 23 will not however be provided with anyprojection such as 25 nor will it cooperate directly with either of thedepressible elements 15.

Pivotally mounted on each of the plunger members 21, 22 and 23 are twocontact carriers 26 each adapted to support a pair of contacts in theform of rollers 27. As will be seen from FIGURE 1 each of the contactcarriers 26 is provided with an upper and a lower arm 26a, 26brespectively such arms being adapted to engage in V- shaped recessesformed respectively in projections 28 and 29 at the upper and lowersides of each plunger member. In FIGURE 2 the aforesaid recesses areshown in the upper projection 29 such recesses being indicated by thereference numeral 30. The contact carriers 26 on each plunger member areconnected by a tension spring 31 which serves to hold said carriers inthe operative or nonoperative position, it being appreciated that when apair of carriers is moved angularly from one limiting position suchmovement will initially tension the spring 31 but as soon as the deadcentre position is passed said spring will be effective to snap saidcontact carriers into the other limiting position.

The fixed contacts 20 are rivetted in pairs on contact holders 32 whichare formed of plastic or other appropriate dielectric material and areheld in place on the respective pressings 18, 19 by means of nuts andbolts such as are indicated at 33. Associated with each contact is anelement 34 which acts as a washer for the rivetted or turned over headof the contact and is formed with a blade like portion 34a to whichcurrent supply leads are connected.

The unit illustrated in the drawings is suitable for controlling a twospeed reversible electric motor and in this particular case the contactholder 32 mounted on the pressing 18 is fitted with three sets each offour contacts i.e. two pairs of fixed contacts in respect of each of theplunger members 21, 22 and 23. The contact holder carried by thepressing 19 is on the other hand fitted with only one set of fourcontacts 20 with which the plunger member 22 will cooperate but in orderto maintain the geometry of the unit-correctly it is also fitted withtwo sets of dummy insulating strips 35 with which the rollers 27 on thecontact carriers 26 of the plunger members 21 and 23 will be in contactwhen said plunger members are inoperative.

In order to prevent depression of the other element and actuation of itsassociated plunger member 21 or 23 when one of such elements is alreadydepressed an interlock device is incorporated which will be effective ondisplacement of one of said plunger members to be moved thereby into aposition wherein it will prevent actuation of said other plunger member.In the embodiment such an interlock device comprises a rod 36 ofrectangular section such rod which is slidably supported in guides onthe pressing 18 having wedged shaped ends adapted to function as camsurfaces. The shank portion of each plunger 21, 23, carrying a pushbutton element 15 is formed with a slot which provides a cam or beveledsurface adapted to cooperate with the cam surface on the appropriate endof the bar 36. When the switch is inoperative the beveled end of the bar36 will be in engagement with the slot in the shank of the plungermember last inoperativei.e., plunger 23 in FIGURE 3, so that plunger 21is free to be depressed. On the other hand, if plunger 23 is depressedthe bar will move longitudinally until the other beveled end is in itscorresponding slot in the shank of plunger 21 leaving plunger 23 free tobe depressed. If plunger 21 is then depressed while plunger 23 isdepressed, the shank of plunger 23 will prevent axial displacement ofthe bar 36. Thus, the depression of one of said plunger members 21 or 23will result in axial displacement of said rod so that it will positivelyprevent depression of the second member- To avoid loading the currentcarrying cable to which the switch assembly is attached, a loop 37 isattached to the central portion 11 of the outer casing, such loopallowing for the attachment of a wire rope or chain which will beeifective actually to support the switch assembly, said rope or chainbeing shorter than the cable so that the latter will always remain slackand not be submitted to any undesirable pulling.

It will be noted that the cable sleeve 14 is so designed that it mayreadily be cut to suit cables of different diameters. It will be notedthat the supply cable introduced through the sleeve 14 will be clampedin place by means of acable clamp 38 which is carried by a bracket 39attached to the pressings 18, 19.

The assembly above described is adapted to operate as follows:

If either of the elements 15 is depressed the appropriate plunger member21 or 23 will be moved inwardly against the action of its spring 24 andif the extent of the depression is sufficient the contact carriers 26associated with that member will be caused to pass over the dead centreposition and snap into an operative position wherein the contact rollers27 will bridge the appropriate fixed contacts 20. As will be seen fromthe wiring diagram of FIGURE 4 such an operation will result incompletion of the circuit for one set of windings of the reversibleelectric motor which is indicated at 40. As will be seen at this stagethe roller contacts 27 associated with the centre plunger member 22 willalready be bridging a pair of fixed contacts 20 (i.e. the contactscarried by the pressing 19). Upon further depression of the element 15the projection 25 on the appropriate plunger member (i.e. the plungermember 21 or 23 which was initially displaced) will engage the middleplunger member 22 and will force the same rearwardly against the actionof its spring 24, with resultant snapping over of its contact carriers26 to bring the respective roller contacts 27 into engagement with theappropriate set of contacts 20 carried by the pressing 18. With thefirst setof contacts 20 still closed as a result of the action of theplunger member 21 or 23 as the case may be it will be appreciated onreference to the diagram of FIGURE 4 that actuation of the plungermember 22 will result in energisation of the other motor windings and inincrease of the motor speed. It is to be understood that the fixedcontacts 20 appropriate to the plunger member 21 and the contacts 20appropriate to the plunger member 23 are respectively so connected thaton closure they will cause rotation of the motor in opposite directions.As will be seen from the diagram of FIGURE 4 the brake coil which isdesignated by 41 will remain energised during change-over from one motorspeed to the other whatever the direction of rotation of the motor.

As hereinbefore indicated the switch assembly above described issuitable for control of a two speed reversible motor such as is commonlyemployed in hoist equipment. Clearly the assembly could readily beadapted for single speed motor control by omitting the central plungermember 22 and its associated components and/or it thought necessary bylimiting the travel of the plunger members 21, 23.

Alternatively by appropriately increasing the length of the pressings18, 19 and of course the casing part 11 it would be possible to providefor an increase in the number of plunger members incorporated in theswitch unit. Provision may be made for any number of plunger members upto say eight with the associated fixed contacts and appropriateprovision of switch operating elements 15 in the casing part 11. Withthe construction described it will be feasible to produce the pressings18, 19 and components of the casing part 11 in relatively long stripsfrom which appropriately dimensionedlengths may be cut off as required.In FIGURES 5 and 6 there is illustrated a pressed strip from whichsections of appropriate length may be cut to form the fronts of easingparts 11. The strip of FIGURES 5 and 6 is of channel or U section and isprovided with apertures 40 each adapted to accommodate a depressibleswitch operating element such as 15. To provide for the completion ofcasing parts 11 a further channel or U section strip will be providedsuch strip being complementary to that shown in FIGURES 5 and 6 butwithout the apertures 40. To form a casing part 11 a selected length ofthe apertured strip shown in FIGURES 5 and 6 will be cut off togetherwith a corresponding length of complementary but unapertured stripwhereafter the two cut lengths will be appropriately applied one to theother and welded together to 'form an open ended hollow sleeve whichwill constitute the required casing part 11. Thus it will be appreciatedthat switch assemblies incorporating any desired combination of pushbuttons may readily be produced and since the resulting unit will berelatively slender it will be capable of being readily held andmanipulated in and by one hand, thus leaving the other hand of theoperator free for load control or other purposes. Furthermore in view ofthe clear marking of the depressible elements or push buttons it will bereadily apparent to any operator which element requires to be depressedto obtain the desired functioning of any motors with which the switchassembly is associated.

What I claim is:

1. A switch unit comprising:

two elongated, relatively thin, strip-like elements, the

"two elements being parallel with their longitudinal faces beingspacedly and oppositely disposed from each other;

at least two pairs of fixed electrical contacts mounted on the face ofat least one support element at longitudinally spaced positions thereon,each pair of fixed electrical contacts being operatively associated witha pair of contact carriers mounted on a plunger;

means mounted on strip-like elements for supporting at least two plungermembers for sliding movement transversely with respect to the faces ofthe supporting elements;

at least two plunger members supported by the plunger support means; and

a pair of contact carriers, having contacts carried thereby, pivotallymounted on each plunger member in such manner so as to be disposed inthe space between the support elements, the contact carriersbeing springloaded and so arranged on their respective plunger members that uponappropriate depression of either plunger member the contact carriersassociated therewith will be moved angularly past a dead center positionwhereafter the spring will be effective to cause them to snap into aposition wherein the contacts carried thereby will bridge theappropriate pair of fixed contacts carried by the support element.

2. A switch unit as in claim 1 wherein the support members, plungermembers and associated parts are housed within an outer casing, theouter casing being equipped with at least one depressible elementarranged to cooperate with one plunger member.

3. A switch unit as in claim 1 including resilient means associated witheach plunger member adapted normally to maintain each plunger member inan initial position such that the contacts carried by the contactcarriers will be out of contact with the appropriate pair of fixedcontacts, the arrangement being such that depression of the plungermember will take place against the action of said resilient means whichwill be effective to restore said plunger member to its initial positionon removal of pressure from the plunger member.

4. A switch unit as in claim 1 in which one of the plunger members ismounted so as to be operatively connected to the second plunger member,the second plunger member having a lateral projection with its outerfree end positioned within the path of movement of the first plungermember, whereby initial depression of the secnd plunger member bringsits movable contacts into engagement with the appropriate pair of fixedcontacts and brings the projection into engagement with the firstplunger member, and further depression of the second plunger membercauses the first plunger member to be likewise depressed and effectmovement of its movable contacts into engagement with its associatedfixed contacts.

5. A switch unit as in claim 1 including an additional plunger membermounted by the support elements and in operative engagement with atleast two other plunger members, the additional plunger member having apair of contact carriers, with contacts carried thereby, pivotallymounted thereon, the contact carriers being spring loaded and soarranged that they are normally adapted to be disposed from a pair offixed contacts mounted on the support elements, the two other plungermembers each having a lateral projection with its outer free endpositioned within the path of movement of the additional plunger member,whereby initial depression of either of the two other plunger membersbrings its movable contacts into engagement with the appropriate pair offixed contacts and brings its projection into engagement with theadditional plunger member and further depression of the initiallydepressed plunger member causes the additional plunger member to belikewise depressed and effect movement of its movable contacts intoengagement with its associated fixed contacts.

6. A switch unit as in claim 5 including interlocking means operativelyassociated with the two plunger members for positively preventingactuation of one of the two plunger members.

7. A switch unit comprising:

support means comprising at least two parallel faces spacedly andoppositely disposed from each other and facing each other;

at least two pairs of fixed electrical contacts mounted on at least oneface of the supporting means at longitudinally spaced positions, eachpair of fixed electrical contacts being operatively associated with apair of contact carriers mounted on a plunger;

means on the support means for supporting at least two plunger membersfor sliding movement transversely with respect to the faces of thesupport means;

at least two plunger members supported by the plunger support means, afirst plunger member having a lateral projection with its outer free endpositioned within the path of movement of the second plunger member anddisposed therefrom in its non-operative position; and

a pair of contact carriers, h-aving contacts carried thereby, pivotallymounted on each plunger member in such a manner so as to be disposed inthe space between the support means, the contact carriers being springloaded and so arranged on their respective plunger members that uponappropriate depression of either plunger member the contact carriersassociated therewith will be moved angularly past a dead center positionwhereafter the spring will be effective to cause them to snap into aposition wherein the contacts carried thereby will bridge theappropriate pair of fixed contacts carried by the support means, wherebyinitial depression of the first plunger member brings its moveablecontacts into engagement with the appropriate pair of fixed contacts andbrings the projection into engagement with the second plunger member andfurther depression of the first plunger member causes the second plungermember to be likewise depressed and effect movement of its movablecontacts into engagement with its associated fixed contacts.

8. The switch unit as in claim 7 wherein the support means comprises twoelongated, relatively thin, striplike elements, the two elements beingparallel with their longitudinal faces being spacedly and oppositelydisposed from each other, and the two pair of fixed electrical contactsbeing mounted over the face of at least one support element atlongitudinally spaced positions thereon.

9. The switch unit as defined in claim 7 additionally comprising a thirdplunger member identical to the first plunger member and having aprojection likewise disposed from and extending into the path ofmovement of the second plunger member whereby initial depression ofeither the first or third plunger member brings its moveable contactsinto engagement with the appropriate pair of fixed contacts and bringsthe projection into engagement with the second plunger member andfurther depression of this plunger member causes the second plung ormember to be likewise depressed and effect movement of its moveablecontacts into engagement with its associated fixed contacts.

10. The switch unit as in claim 9 including interlocking means extendingbetween the first and third plunger members for positively preventingactuation of one of the plunger members when the other plunger member isdepressed.

11. The switch unit as in claim 7 wherein the support means, plungermembers and associated parts are housed within an outer casing, theouter casing being equipped with at least one depressible elementarranged to cooperate With the plunger member having the projection.

pressible element is made of resilient material.

13. The switch unit as in claim 7 including resilient means associatedwith each plunger member adapted normally to maintain each plungermember in an initial position such that the contacts carried by thecontact carriers will be out of contact with the appropriate pair offixed contacts, the arrangement being such that depression of theplunger member will take .place against the action of said resilientmeans which will be effective to restore said plunger member to itsinitial position on removal of pressure from the plunger member.

8 14. A switch unit as in claim 7 including a second pair of fixedcontacts engageable by the contacts of the second plunger member in itsnormal position, the two pairs of fixed contacts associated with thesecond plunger member providing for variations in the electrical circuitin which the switch unit is incorporated.

No references cited.

ROBERT K. SCHAEFER, Primary Examiner.

D. SMITH, Assistant Examiner.

1. A SWITCH UNIT COMPRISING: TWO ELONGATED, RELATIVELY THIN, STRIP-LIKEELEMENTS, THE TWO ELEMENTS BEING PARALLEL WITH THEIR LONGITUDINAL FACESBEING SPACEDLY AND OPPOSITELY DISPOSED FROM EACH OTHER; AT LEAST TWOPAIRS OF FIXED ELECTRICAL CONTACTS MOUNTED ON THE FACE OF AT LEAST ONESUPPORT ELEMENT AT LONGITUDINALLY SPACED POSITIONS THEREON, EACH PAIR OFFIXED ELECTRICAL CONTACTS BEING OPERATIVELY ASSOCIATED WITH A PAIR OFCONTACT CARRIERS MOUNTED ON A PLUNGER; MEANS MOUNTED ON STRIP-LIKEELEMENTS FOR SUPPORTING AT LEAST TWO PLUNGER MEMBERS FOR SLIDINGMOVEMENT TRANSVERSELY WITH RESPECT TO THE FACES OF THE SUPPORTINGELEMENTS; AT LEAST TWO PLUNGER MEMBERS SUPPORTED BY THE PLUNGER SUPPORTMEANS; AND A PAIR OF CONTACT CARRIERS, HAVING CONTACTS CARRIED THEREBY,PIVOTALLY MOUNTED ON EACH PLUNGER MEMBER IN SUCH MANNER SO AS TO BEDISPOSED IN THE SPACE BETWEEN THE SUPPORT ELEMENTS, THE CONTACT CARRIERSBEING SPRING LOADED AND SO ARRANGED ON THEIR RESPECTIVE PLUNGER MEMBERSTHAT UPON APPROPRIATE DEPRESSION OF EITHER PLUNGER MEMBER THE CONTACTCARRIERS ASSOCIATED THEREWITH WILL BE MOVED ANGULARLY PAST A DEAD CENTERPOSITION WHEREAFTER THE SPRING WILL BE EFFECTIVE TO CAUSE THEM TO SNAPINTO A POSITION WHEREIN THE CONTACTS CARRIED THEREBY WILL BRIDGE THEAPPROPRIATE PAIR OF FIXED CONTACTS CARRIED BY THE SUPPORT ELEMENT.